1. Field of the Invention
The present invention relates generally to an axle carrier for use in an axle assembly and, more particularly, to an axle carrier trunnion having a stepped bore.
2. Related Art
Carrier-type axle housing assemblies, commonly referred to as a Salisbury designs, have been utilized in the automotive industry for some time. With this type of axle housing, an axle tube is pressed into each one of a pair of carrier trunnions, with each tube being plug welded to the carrier through radially extending holes formed in the corresponding carrier trunnion. An additional hole is formed in each trunnion for purposes of spreading the carrier in order to properly preload the differential bearing during installation of the differential which is housed within the carrier. The carrier trunnions require strength to withstand, or carry stress from two primary sources: the hoop stress resulting from the interference fit between the axle tube and the trunnion; and the bending stress resulting from the suspension loads of the vehicle, caused by forces applied at the spring attachments and wheels. More recently, cast aluminum or other non-ferrous alloys have been utilized to manufacture the axle carriers in place of cast iron in response to customer demands for weight reduction, and the associated increase in fuel efficiency of the vehicle. The puddle weld holes, spreader holes, and the outboard ends of the trunnions are locations of stress concentration, and accordingly, have been known to comprise fracture origin cites during overload testing of aluminum axle carriers. Accordingly, at the time of the present invention, automotive design engineers continue to search for new and improved axle carriers having comparable strength but reduced weight as compared to prior, ferrous material axle carriers.